Illumination tube



March 10, 1936. E.'A. GIARD 2,033,375

. ILLUMINATION TUBE Filed April 20, 1955 Patented Mar. 10, 1936 UNITED STATES IILUMINATION TUBE EugeneA. Giard,, Milwaukee, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Application April 20, 1933, Serial No. 667,019

'IClaims.

This invention relates to improvements in gaseous illuminating tubes employed for lighting eifects.

An object of the invention is to provide a tube which will respond to an ignition voltage lower than the normal operating voltage of the tube. Another object is to provide a gaseous illuminating tube, the light emission or brilliancy of which can be varied within very wide limits by varying the voltages impressed upon the tube.

Another object is to provide a tube which yields a steady light for a wide range of brilliancy.

Another object is to provide a tube which emits a steady light from a very low to the highest brilliancy at'which the tube operates.

Other objects and advantages of the invention will hereinafter appear.

The ordinary neon or other gaseous tube is equipped with two cold electrodes and initiation of discharge therebetween depends upon the presence of a few ionized molecules which are present in the tube at all times and which permit initia tion of discharge through the tube when the potential difference between the electrodes is sumciently high. If the tube is supplied with current from an alternating current source, the discharge is started during each half cycle at a moment when a suflicient voltage exists between the electrodes to produce adequate additional ionization of the gas to maintain an arc. The voltage which is necessary to maintain the gas column between the electrodes ionized or in the conducting state, is usually appreciably less than that which is required to start the ionization or discharge.

If an attempt is made to reduce the voltage applied to the tube after the arc has started, for the purpose of reducing the luminosity of the arc, the arc is extinguished and is not ignited again until the voltage reaches a higher value. The voltages at which this occurs are not always the same, on account of the random ionization of the gas in the neighborhood of the electrodes and also due to voltage fluctuations and transient voltages on the supply lines. It has, therefore,

not been possible, in the past, to dim neon and similar tubes from full brilliancy to black or vice versa. Ordinary gas tubes flicker when operating at their lowest brilliancy, because at the start of each half cycle of the voltage is is necessary to ionize enough gas to start the arc, and due to irregularities the arc does not always start at the same voltage. Hence its establishment at the lower operating voltage is not certain and this causes flickering.

The present invention avoids this instability by providing a definite and controlled quantity of ionized gas around the main electrodes prior to the establishment of the are between the main electrodes.

The accompanying drawing illustrates dia- 5 grammatically one embodiment of my invention.

In the drawing, I is a gaseous luminous tube having at its ends enlargements 2 and 3 in which are mounted main electrodes 4 and 5, respectively, and auxiliary electrodes 6 and 1, respectively. These electrodes may be of any suitable form. Connected between the auxiliary electrodes 6 and 1 is a resistor 8 of high ohmic value. A transformer 9 has its primary winding l0 connected across alternating current supply lines II and I! in series with a regulating impedance l3, the secondary winding I4 of said transformer being connected between the main electrodes 4 and 5.

The operation of the tube is as follows: When voltage is supplied to the transformer I0 and said voltage is gradually raised from a minimum by adjustment of the impedance I3, a point is reached where the gas between the electrodes 46 and 5-4, respectively, at the two ends of the tube becomes sufficiently ionized to sustain a continuous discharge in the two ends of the tube, current flowing from the winding M between the electrodes 4 and 6 through the resistance 8, between the electrodes 1 and 5 back to the winding M, or in the opposite direction during alternate half cycles. This discharge, which is limited by the high resistance 8, provides a supply of ionized molecules around the main electrodes tending to ionize additional gas molecules by impact. Further increase in the applied voltage so increases the number of these ionized molecules that they are forced more and more into the cylindrical main portion of the tube. until the luminous columnsv emerging from both ends flll the entire central part of the tube. The intensity of the light under these conditions is very low compared to the minimum intensity of the light which can be maintained continuously in an ordinary luminous tube without the auxiliary electrodes.

Further increase of the voltage impressed upon the main electrodes increases the intensity or the light emitted from the main column, while the discharge in the tube ends between the main light column at which the tube can be operated with a steady light emission is very much lower than the minimum intensity of an ordinary tube when operated without flickering.

As aforedescribed, the resistance 8 should be as high as possible, permitting just a sufiicient amount of discharge between the respective main and auxiliary electrodes to'supply an adequate amount of ionization for the formation of the main light column.

The voltage impressed upon the main electrodes may, of course, be varied in any other suitable manner and it is also possible to operate the tube with a variable voltage direct current in which case the auxiliary electrode, at the positive end of the tube, may be omitted and the resistance 8 be joined directly tothe main anode.

The main body of the t e need not be cylindrical as shown in the dra ng, but may assume any other desired form suitable for the purpose.

It is obvious that a single gas or a mixture of gases or a vapor or mixture of vapors and/or gases may be employed in the tube described.

What I claim as new and desire to secure by Letters Patent is:

1. A luminous gas discharge tube, comprising a glass tube having enlarged electrode chambers, a main electrode and an auxiliary electrode within each chamber and a relatively high impedance arranged externally of said tube andconnected in circuit between said auxiliary electrodes.

2. A luminous gas discharge light, comprising a glass tube havingenlarged electrode chambers and a restricted passage therebetween, an attenuated gas in said tube, a main electrode and an auxiliary electrode wholly within each chamber of said tube and a relatively high impedance arranged externally of said tube and connected in circuit between said auxiliary electrodes.

3. A luminous gas discharge light, comprising an hermetically sealed glass tube having enlarged electrode chambers and a restricted passage therebetween, an attenuated gas in said tube, a main electrode in each chamber of said tube adapted to be connected respectively to opposite poles of a power supply, an auxiliary electrode wholly within each chamber, and a relatively high-impedance series connection between said auxiliary electrodes arranged externally of said tube.

. 4. A luminous gas discharge light, comprising an hermetically sealed glass tube having an enlarged electrode chamber at each end-and a restricted passage therebetween, an attenuated gas in said tube, a main electrode in each chamber adapted to be connected respectively to the poles of a power supply, an auxiliary electrode wholly within each chamber and an external relatively high impedance series connection for said auxiliary electrodes.

5. A luminous gas discharge light, comprising an hermetically sealed glass tube having an'enlarged electrode chamber at each end and a restricted passage therebetween, an attenuated gas in said tube, a main electrode ineach chamber adapted to be connected respectively to the poles of a variable voltage source of power, an auxiliary electrode wholly within each chamber'and an external series connection for said auxiliary electrodes 01 relatively high impedance.

6. A luminous gas" discharge tube, comprising a glass tube having in a spaced relation enlarged electrode chambers, main electrodes within said chambers for emitting a discharge and auxiliary electrodes through which the discharge between 

